ABC said the parliamentary elections in December had produced a sharp gain in public optimism that the US was making progress in Iraq, but the slide towards civil war has erased those gains just as quickly.
The Washington Post said more than seven in 10 Republicans and eight in 10 Democrats and political independents believe civil war is coming, showing that the public's assessment of the situation cuts across party lines.
About one third of Americans polled thought such a conflict was "very likely" to occur, the newspaper said.
The surge in violence has killed more than 500 people since the destruction of a major Shia shrine in Samarra on 22 February.
Fifty-five per cent of poll respondents said the US was not making significant progress restoring civil order in Iraq - up 19 points from a poll shortly after the December elections.
Nearly half, or 49%, said they thought there has been progress in establishing a democratic government in Iraq. But that was down from 65% in December.
Nearly three months after Iraqis elected a parliament, Iraq's political leaders are still fighting over the post of prime minister, delaying the formation of a grand coalition government, which Washington promoted in the hope of fostering stability and allowing US troops to begin withdrawing.
According to the poll, a record 65% of Americans think the Bush administration lacks a clear plan for what to do in Iraq.
Despite the bleak views of the situation in Iraq, fewer than 20% of respondents support an immediate withdrawal of all US troops, while a narrow majority, 52%, supported decreasing troop strength.
Fifty-nine percent of those polled said they disapprove of the way the American president is handling the situation in Iraq, compared with 40% approval - nearly unchanged from the same poll's numbers in late January.
George Bush's overall job approval rating was steady at 41%, unchanged, but two points above his career low in a poll last fall.
The telephone poll of 1000 people was conducted on 2-5 March and has a three-point error margin.